The CAS Registry Mumber 4353-40-6 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 4,3,5 and 3 respectively; the second part has 2 digits, 4 and 0 respectively. Calculate Digit Verification of CAS Registry Number 4353-40: (6*4)+(5*3)+(4*5)+(3*3)+(2*4)+(1*0)=76 76 % 10 = 6 So 4353-40-6 is a valid CAS Registry Number.